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Multiple-Input Multiple-Output (MIMO)

The use of Multiple-Input Multiple-Output (MIMO) techniques has revolutionized wireless communications systems with potential gains in capacity when using multiple antennas at both transmitter and receiver ends of a communications system. New techniques, which account for the extra spatial dimension, have been adopted to realize these gains in new and previously existing systems.

MIMO technology has been adopted in multiple wireless systems, including Wi-Fi, WiMAX, LTE, and LTE-Advanced.

The Communications Toolbox™ product offers components to model:

  • OSTBC (orthogonal space-time block coding technique)

  • MIMO Fading Channels

  • Spherical Decoding

and demos highlighting the use of these components in applications.

For background material on the subject of MIMO systems, see the works listed in Selected Bibliography for MIMO systems.

Orthogonal Space-Time Block Codes (OSTBC)

The Communications Toolbox product provides components to model Orthogonal Space Time Block Coding (OSTBC) – a MIMO technique which offers full spatial diversity gain with extremely simple single-symbol maximum likelihood decoding [4,6,8].

In Simulink®, the OSTBC Encoder and OSTBC Combiner blocks, residing in the MIMO block library, implement the orthogonal space time block coding technique. These two blocks offer a variety of specific codes (with different rates) for up to 4 transmit and 8 receive antenna systems. The encoder block is used at the transmitter to map symbols to multiple antennas while the combiner block is used at the receiver to extract the soft information per symbol using the received signal and the channel state information. You access the MIMO library by double clicking the icon in the main Communications Toolbox block library. Alternatively, you can type commmimo at the MATLAB command line.

The OSTBC technique is an attractive scheme because it can achieve the full (maximum) spatial diversity order and have symbol-wise maximum-likelihood (ML) decoding. For more information pertaining to the algorithmic details and the specific codes implemented, see OSTBC Combining Algorithms on the OSTBC Combiner block help page and OSTBC Encoding Algorithms on the OSTBC Encoder block help page. Similar functionality is available in MATLAB® by using the comm.OSTBCCombiner and comm.OSTBCEncoder System objects.

MIMO Fading Channel

The Communications Toolbox software includes a MIMO fading channel object. You can use this object to model the fading channel characteristics of MIMO links. The object models both Rayleigh and Rician fading, and uses the Kronecker model for the spatial correlation between the links [1].

For more information, see the comm.MIMOChannel.

Spherical Decoding

The Communications Toolbox software includes a sphere decoder System object™. You can use this object to find the maximum-likelihood solution for a set of received symbols over a MIMO channel with any number transmit antennas and receive antennas.

For more information, see the comm.SphereDecoder reference page.

Selected Bibliography for MIMO systems

[1] C. Oestges and B. Clerckx, MIMO Wireless Communications: From Real-World Propagation to Space-Time Code Design, Academic Press, 2007.

[2] George Tsoulos, Ed., "MIMO System Technology for Wireless Communications", CRC Press, Boca Raton, FL, 2006.

[3] L. M. Correira, Ed., Mobile Broadband Multimedia Networks: Techniques, Models and Tools for 4G, Academic Press, 2006.

[4] M. Jankiraman, "Space-time codes and MIMO systems", Artech House, Boston, 2004.

[5] G. J. Foschini, M. J. Gans, "On the limits of wireless communications in a fading environment when using multiple antennas", IEEE Wireless Personal Communications, Vol. 6, Mar. 1998, pp. 311-335.

[6] S. M. Alamouti, “A simple transmit diversity technique for wireless communications,” IEEE Journal on Selected Areas in Communications, vol. 16, no. 8, pp. 1451–1458, Oct. 1998.

[7] V. Tarokh, N. Seshadri, and A. R. Calderbank, “Space–time codes for high data rate wireless communication: Performance analysis and code construction,” IEEE Transactions on Information Theory, vol. 44, no. 2, pp. 744–765, Mar. 1998.

[8] V. Tarokh, H. Jafarkhani, and A. R. Calderbank, “Space-time block codes from orthogonal designs,” IEEE Transactions on Information Theory, vol. 45, no. 5, pp. 1456–1467, Jul. 1999.

[9] 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, Evolved Universal Terrestrial Radio Access (E-UTRA), Base Station (BS) radio transmission and reception, Release 10, 3GPP TS 36.104, v10.0.0, 2010-09.

[10] 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, Evolved Universal Terrestrial Radio Access (E-UTRA), User Equipment (UE) radio transmission and reception, Release 10, 3GPP TS 36.101, v10.0.0, 2010-10.